Sidebar disappears

Am using a theme which has broad sidebars but the left hand bar disappears completely - no side bar at all - when the favourites group is minimised. I do not use this group and for me it just uses up column space. Is there any way to retain the side bar and even better, keep it broad ?

Update on this message.
Left sidebar has mysteriously re-appeared in its original size and with Favourites minimised. Difficult to understand Em C sometimes, and why it randomly changes.

Click on the ‘<’ button [top right corner] to toggle or go into menu>view and choose your preferred setting.

It too has a ‘<’ button.

Thanks for the suggestions. Everything’s working fine right now so I am not going to touch anything !!